1. Field of Use
The present invention relates to an electrostatic charging member, and more specifically, to an outer surface layer of an electrostatic charging member.
2. Background
Image forming apparatuses require electrostatic charging of an image holding member by use of an electrostatic charging member or bias charging member. Electrostatic latent images differing from their surroundings in electric potential are formed on the electrostatically charged image holding member. The electrostatic latent images are developed with a developer containing toner, and eventually transferred to a recording material.
Electrostatic charging members are devices having the function of charging electrostatically image holding members and can use a contact charging method, wherein the charging member is brought into direct contact with the image holding member to perform electrostatically charge of the image holding members.
The electrostatic charging member is equipped with an electrostatic charging member, such as an electrostatic charging roll, which is brought into direct contact with the surface of an image holding member and made to rotate in synchronization with movement of the image holding member's surface, thereby giving electrostatic charges to the image holding member. The electrostatic charging roll is made up of, e.g., a base material and an elastic conducting layer formed around the peripheral surface of the base material and an outer most layer.
Typically, porous polyimide fillers have been used in the outer layer of an electrostatic charging roll. However, there are drawbacks to using porous polyamide fillers. These problems include swelling in organic solvents and the low melting point (about 170-180° C.) of polyimide.
It would be desirable to have a filler for an outer layer of a bias charging roller that provides robust morphology control, does not swell in organic solvents and has a melting point greater than 180° C.